Many electrical devices include chargeable/rechargeable batteries that enable the device to operate, at least temporarily, when not connected to an external power source or when the external power source is disabled, for example, when a power failure occurs. Some of these devices are connected in series to a switch (for example, light switch) which connects or disconnects them to the external power source, such that when external power fails, the device is connected to a battery or batteries. In order to maintain the charge on the batteries, they are typically charged when the switch is off. Typically, a special installation is required, for example, by installation of additional wire to connect the charger to the power source and to provide power to the charger also when the switch is off.
An example of such a device may be dual purpose emergency lighting system that may enable the light source to turn on or off according to the light switch, but activate the light source to work on battery power when there is a power failure.
FIG. 1 illustrates a currently available dual purpose emergency lighting system 200. System 200 may include a power source 22, a light switch 20, a charger 24, a chargeable battery 26, an optional voltage converter 27, an electronic regulation mechanism 28, for example, a DPDT relay, a relay switch 25 and a lamp or other light source 29. When power source 22 is active, regulation mechanism 28 may operate switch 25 to connect light source 29, for example, in series, to light switch 20, thus enabling light source 29 to operate according to the position of switch 20. Charger 24 may be connected to power source 22 through a separate wire not connected to light switch 20, and thus may charge battery 26 with no dependency in the state of light switch 20. When power source 22 is not active, the regulation mechanism 28 may be deactivated, thus connecting light source 29 to the output of voltage converter 27. Voltage converter 27 may optionally be used to boost up the low voltage of battery 26, to match the type and specifications of light source 29. During a power failure battery 26 may be discharged by voltage converter 27 in order to power light source 29. When the power failure ends, regulation mechanism 28 may reconnect light source 29 to light switch 20 and charger 24 may start charging battery 26 to full capacity.
It will be clarified that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.